Effect of physical and chemical structures of graphene oxide on water permeation in graphene oxide membranes

Water permeation through stacked graphene oxide (GO) membranes is a key for its promising potential for filtration and purification applications. The permeation in GO membranes prepared with different physical and chemical structures (GO flakes) varies significantly, which requires to be elucidated. Here, we fabricated four types of GO flakes with different physical and chemical structure by modified Hummers method with controlling of temperature. The results showed a sensitive temperature dependence of the size and oxygen content of the GO flakes. The flake size is negatively correlated with water flux and has a far higher effect on permeation compared with that of the oxygen content. The GO membrane made of the smallest flakes exhibits ultrahigh water flux of up to ~53.7 L m−2 h−1 bar−1, which is more than three times that of conventional large GO membranes, while still maintaining a high rejection rate of ~95.7% for pararosaniline. Importantly, of all pristine GO membranes without any chemical modifications, this is the most permeable membrane for dyes. Our study reveals a sensitive effect of the physical and chemical structures of GO on water permeation and represents a facile step regarding ultrahigh flux GO membranes for water purification.